Self-attaching female fastener elements, including pierce and clinch nuts, are well known in the art. Such self-attaching female fastener elements may be formed either by rolling techniques, wherein the self-attaching female fastener element is generally rectangular including a rectangular projecting pilot portion and flange portions on opposed sides of the pilot portion, or by cold heading techniques, wherein the female fastener element includes a body portion having a bore therethrough and a tubular barrel portion integral with the body portion having a distal open end and a longitudinal axis coincident with the longitudinal axis of the bore through the body portion. The female fastener elements formed by cold header techniques are sometimes referred to as “round” pierce nuts. U.S. Pat. Nos. 4,610,072 and 4,711,021 assigned to the predecessor in interest of this application disclose round pierce nuts of this type and methods of installation.
During installation of a conventional round pierce nut formed by cold header techniques, the distal open end of the tubular barrel portion is received through an opening in a metal panel and substantially simultaneously deformed radially outwardly and axially into a U-shape in cross section to entrap panel metal surrounding the panel opening to permanently attach the female fastener element to the panel. This type of round pierce nut formed by cold header techniques has been commercially successful in mass production applications used by the automotive and appliance industries.
Pierce and clinch nuts of the types described above are generally installed in a die press, which may also be utilized to simultaneously form the metal panel to which the pierce or clinch nut is attached. An installation head is generally attached to one die platen or shoe of a die press, typically the upper die platen, and a die member or die “button” is attached to the other die platen, typically the lower die platen. As will be understood by those skilled in the art, however, the orientation of the installation head and the die button may be reversed. The installation head typically includes a feed chute which receives the self-attaching fasteners and feeds the self-attaching fasteners to the installation head. The installation head then includes a reciprocating plunger which installs the self-attaching fastener in a panel with each stroke of the die press. Where the self-attaching fastener is a self-attaching round pierce of clinch nut, as described above, the feed chute is typically a cylindrical flexible tube which receives the round self-attaching fasteners from a high speed hopper. However, as will be understood, the round self-attaching fasteners must first be oriented, generally in the hopper, such that the barrel portion is received in the installation head opposite the panel for installation in the panel by the reciprocating plunger. The requirement for orientation of the self-attaching fastener element significantly reduces the feed rate in the hopper and requires orientation equipment.
It would therefore be desirable for self-attaching fasteners formed by cold header techniques to be symmetrical with respect to the feed direction in the longitudinal axis of the fastener to increase the feed rate to the installation head and eliminate orientation equipment. However, assuming that the self-attaching fastener element included, for example, an integral barrel portion projecting from opposed ends of the body portion, such that the self-attaching fastener is symmetrical, eliminating orientation in the hopper, the tubular barrel portion projecting from the panel creates other problems following installation including, but not limited to, the longitudinal length of the fastener following installation in the panel. The self-attaching female fastener element of this invention solves these problems.